U.S. patent application number 10/187027 was filed with the patent office on 2004-01-01 for electroplating cell with copper acid correction module for substrate interconnect formation.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Kovarsky, Nicolay, Sun, Zhi-Wen.
Application Number | 20040000491 10/187027 |
Document ID | / |
Family ID | 29779979 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000491 |
Kind Code |
A1 |
Kovarsky, Nicolay ; et
al. |
January 1, 2004 |
Electroplating cell with copper acid correction module for
substrate interconnect formation
Abstract
The present invention generally provides an apparatus and method
for neutralizing an acid in a plating solution. The apparatus
generally includes a plating cell having an anolyte compartment
containing an anolyte and a catolyte compartment containing a
catolyte, wherein the anolyte compartment has an anolyte inlet and
an anolyte drain and the catolyte compartment has a catolyte inlet
and a catolyte drain, and a cell membrane disposed in the cell
between the anolyte compartment and the catolyte compartment,
wherein the membrane is selective to hydrogen ions and copper ions.
The apparatus further includes a catolyte storage unit in fluid
communication with the catolyte inlet and an electrochemical device
in fluid communication with the catolyte chamber, the
electrochemical device being configured to receive a portion of
aged catolyte solution and correct a catolyte concentration. The
method generally includes supplying an electrolyte solution to a
copper plating cell, plating copper onto a substrate in the plating
cell with the electrolyte solution, removing aged electrolyte
solution from the plating cell, and neutralizing a portion of the
used electrolyte solution with an electrochemical device.
Inventors: |
Kovarsky, Nicolay;
(Sunnyvale, CA) ; Sun, Zhi-Wen; (San Jose,
CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS, INC.
Legal Affairs Department
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
29779979 |
Appl. No.: |
10/187027 |
Filed: |
June 28, 2002 |
Current U.S.
Class: |
205/291 ;
204/263; 205/295 |
Current CPC
Class: |
C25D 21/18 20130101;
C25D 7/12 20130101; C25D 21/14 20130101 |
Class at
Publication: |
205/291 ;
204/263; 205/295 |
International
Class: |
C25C 007/00; C25D
017/00 |
Claims
1. A copper plating system, comprising: an anolyte compartment,
wherein the anolyte compartment has an anolyte inlet; an anolyte
storage unit in fluid communication with the anolyte inlet; a
catolyte compartment; a catolyte storage unit in fluid
communication with the catolyte inlet; a membrane disposed between
the anolyte compartment and the catolyte compartment, wherein the
membrane is selective to hydrogen ions and copper ions; and a
catolyte electrochemical device in fluid communication with the
catolyte compartment, the catolyte electrochemical device being
configured to correct a catolyte concentration.
2. The copper plating system of claim 1, further comprising an
anolyte electrochemical device in fluid communication with the
anolyte compartment, the anolyte electrochemical device being
configured to correct an anolyte concentration.
3. The copper plating system of claim 1, wherein the catolyte
compartment comprises copper sulfate, sulfuric acid, copper
chloride, and organic additives.
4. The copper plating system of claim 1, wherein the anolyte
compartment comprises copper sulfate and sulfuric acid in an amount
sufficient to provide a pH of from about 2 to about 6.
5. The copper plating system of claim 1, wherein the catolyte
electrochemical device comprises: a housing having a cathode
electrode and an anode electrode; an anode chamber positioned
proximate the anode electrode and between the cathode electrode and
the anode electrode, wherein the anode chamber is configured to
receive aged catolyte solution; a cathode chamber positioned
proximate the cathode electrode and between the cathode electrode
and the anode chamber, wherein the anode chamber is configured to
neutralize acid in the aged catolyte solution; and a bipolar
membrane positioned between the anode chamber and the cathode
chamber configured to remove hydrogen ions from the aged catolyte
solution and provide hydroxide ions to the aged catolyte
solution.
6. The copper plating system of claim 5, wherein the anode
electrode is insoluble and is configured to provide copper ions to
the aged catolyte.
7. The copper plating system of claim 5, wherein the cathode
chamber comprises a cathode chamber fluid inlet and a cathode
chamber fluid outlet configured to circulate sulfuric acid in the
cathode chamber.
8. The copper plating system of claim 1, wherein the catolyte
electrochemical device comprises: a housing having a cathode
electrode positioned in a first end and an anode electrode
positioned in a second end, the second end being oppositely
positioned from the first end; an anode chamber positioned
proximate the anode electrode and between the cathode electrode and
the anode electrode configured to provide copper ions to an aged
catolyte solution; a cathode chamber positioned proximate the
cathode electrode and between the cathode electrode and the anode
chamber configured to neutralize acid in the aged catolyte
solution; and an input chamber positioned between the anode and
cathode chambers and configured to receive the aged catolyte
solution.
9. The copper plating system of claim 8, wherein the input chamber
comprises: a cathodic membrane positioned on a cathode side of the
input chamber configured to receive hydrogen ions from the input
chamber; a cathodic membrane positioned on an anode side of the
input chamber configured to provide copper ions to the input
chamber; and an input chamber fluid outlet configured to dispense
restored electrolyte therefrom.
10. The copper electrochemical plating system of claim 9, wherein
the cathode chamber comprises a cathode chamber fluid inlet and a
cathode chamber fluid outlet configured to circulate sulfuric acid
in the cathode chamber.
11. The copper plating system of claim 9, wherein the anode chamber
comprises an anode chamber fluid inlet and an anode chamber fluid
outlet configured to circulate a copper sulfate solution in the
anode chamber.
12. The copper plating system of claim 9, wherein the cationic
membrane positioned on the cathode side of the input chamber is
selective to hydrogen ions.
13. The copper plating system of claim 8, wherein the input chamber
comprises: a bipolar membrane positioned on a cathode side of the
input chamber configured to receive hydrogen ions from the input
chamber and provide hydroxide ions to the input chamber; a cathodic
membrane positioned on an anode side of the input chamber
configured to provide copper ions to the input chamber; and an
input chamber fluid outlet configured to dispense restored
electrolyte therefrom.
14. The copper plating system of claim 8, wherein the input chamber
comprises: a bipolar membrane positioned on a cathode side of the
input chamber configured to receive hydrogen ions from the input
chamber and provide hydroxide ions to the input chamber; an anodic
membrane positioned on an anode side of the input chamber
configured to receive sulfate ions from the input chamber; an input
chamber fluid outlet configured to dispense restored electrolyte
therefrom; and a control device configured to correct the copper
concentration in the restored electrolyte.
15. The copper plating system of claim 14, wherein copper sulfate
is added to the restored electrolyte in an amount determined by the
control device.
16. The copper plating system of claim 1, wherein the catolyte
electrochemical device comprises: a housing having a cathode
electrode positioned in a first end and an anode electrode
positioned in a second end, the second end being oppositely
positioned from the first end; an anode chamber positioned
proximate the anode and between the cathode electrode and the anode
electrode configured to neutralize acid in the aged catolyte
solution; a cathode chamber positioned proximate the cathode
electrode and between the cathode electrode and the anode chamber
configured to neutralize acid in the aged catolyte solution; at
least one input chamber positioned between the cathode electrode
and the anode chamber configured to receive aged catolyte; at least
one copper feed chamber positioned between the input chamber and
the anode chamber configured to provide copper ions to the aged
catolyte; and at least one isolation chamber positioned between the
input chamber and the copper feed chamber to neutralize acid in the
aged catolyte solution.
17. The copper plating system of claim 16, wherein the copper feed
chamber comprises a feed chamber fluid inlet and a feed chamber
fluid outlet configured to circulate copper sulfate in the copper
feed chamber.
18. The copper plating system of claim 16, wherein sulfuric acid is
circulated between the isolation chamber, the anode chamber, and
the cathode chamber.
19. The copper plating system of claim 16, wherein a copper sulfate
solution is added to the restored catolyte.
20. The copper plating system of claim 16, wherein the anode
electrode is insoluble.
21. The copper plating system of claim 16, wherein the input
chamber comprises: an anionic membrane positioned on a cathode side
of the anode chamber configured to receive sulfate ions from the
copper feed chamber; a cationic membrane positioned between the
copper feed chamber and the input chamber configured to provide
copper ions to the input chamber; a bipolar membrane positioned
between the input chamber and the isolation chamber configured to
proved hydroxide ions to the input chamber and to receive hydroxide
ions from the input chamber; an anionic membrane positioned between
the isolation chamber and the feed chamber configured to receive
sulfate ions from the feed chamber; and a bipolar membrane
positioned between the cathode chamber and the feed chamber
configured to provide hydroxide ions to the input chamber and
receive hydrogen ions from the input chamber.
22. The copper plating system of claim 1, wherein the catolyte
electrochemical device comprises: a housing having a cathode
electrode positioned in a first end and an anode electrode
positioned in a second end, the second end being oppositely
positioned from the first end; an anode chamber positioned
proximate the anode and between the cathode electrode and the anode
electrode configured to neutralize acid in the aged catolyte
solution; a cathode chamber positioned proximate the cathode
electrode and between the cathode electrode and the anode chamber
configured to neutralize acid in the aged catolyte solution; at
least one input chamber positioned between the cathode electrode
and the anode chamber configured to receive aged catolyte; and at
least one purification chamber positioned between the input
chambers to neutralize acid in the aged catolyte solution.
23. The copper plating system of claim 22, wherein sulfuric acid is
circulated between the anode chamber, the purification chamber, and
the cathode chamber.
24. The copper plating system of claim 22, wherein a copper sulfate
solution is added to the restored catolyte.
25. The copper plating system of claim 22, wherein the anode
electrode is insoluble.
26. The copper plating system of claim 22, wherein the input
chamber comprises: an anionic membrane positioned on a cathode side
of the anode chamber configured to receive sulfate ions from the
input chamber; a bipolar membrane positioned between the input
chamber and the purification chamber configured to provide
hydroxide ions to the input chamber and to receive hydroxide ions
from the input chamber; an anionic membrane positioned between the
purification chamber and the input chamber configured to receive
sulfate ions from the input chamber; and an anionic membrane
positioned between the cathode chamber and the purification chamber
configured to provide hydroxide ions to the purification
chamber.
27. The copper plating system of claim 22, further comprising an
electrodialysis chamber configured to remove contaminants from the
restored catolyte.
28. The copper plating system of claim 22, further comprising a
catolyte storage tank in fluid communication with a catolyte
electrochemical device configured to receive a portion of catolyte
solution and correct a catolyte concentration.
29. The copper plating system of claim 22, further comprising a
column comprising copper oxide in fluid communication with the
anode chamber configured to correct an anolyte concentration.
30. A method for plating copper, comprising: supplying an
electrolyte solution to a copper plating cell; plating copper onto
a substrate in the plating cell with the electrolyte solution;
removing aged electrolyte solution from the plating cell; and
neutralizing a portion of the aged electrolyte solution with an
electrochemical device.
31. The method of claim 30, wherein neutralizing a portion of the
aged electrolyte with an electrochemical device comprises:
receiving the aged electrolyte solution in a first end of a anode
chamber; urging positive copper ions to diffuse from a soluble
anode into the aged electrolyte solution; urging positive hydrogen
ions to diffuse through a bipolar membrane towards a cathode into a
cathode chamber; urging negative hydroxide ions to diffuse through
the bipolar membrane towards an anode into the anode chamber; and
removing a copper sulfate solution from the concentration
chamber.
32. The method of claim 31, wherein the urging steps comprise
applying an electrical bias across the electrodialysis cell.
33. The method of claim 31, further comprising circulating a
sulfuric acid solution through the cathode chamber.
34. The method of claim 30, wherein neutralizing a portion of the
aged electrolyte with an electrochemical device comprises:
receiving the aged electrolyte solution in a first end of an input
chamber; urging positive copper ions to diffuse from a soluble
anode in an anode chamber through a cationic membrane into the aged
electrolyte solution; urging positive hydrogen ions to diffuse
through a cationic membrane towards a cathode into a cathode
chamber; and removing a copper sulfate solution from the
concentration chamber.
35. The method of claim 34, wherein the urging steps comprise
applying an electrical bias across the electrochemical device.
36. The method of claim 34, further comprising circulating a
sulfuric acid solution through the cathode chamber.
37. The method of claim 31, wherein neutralizing a portion of the
aged electrolyte with an electrochemical device comprises:
receiving the aged electrolyte solution in a first end of an input
chamber; urging negative sulfate ions to diffuse through an anionic
membrane towards an anode into an anode chamber; urging positive
hydrogen ions to diffuse through a bipolar membrane towards a
cathode into a cathode chamber; and urging negative hydrogen ions
to diffuse through the bipolar membrane away from the cathode into
the input chamber; and removing a copper sulfate solution from the
concentration chamber.
38. The method of claim 37, wherein the urging steps comprise
applying an electrical bias across the electrochemical device.
39. The method of claim 37, further comprising circulating a
sulfuric acid solution through the cathode chamber.
40. The method of claim 37, further comprising adding a copper
sulfate solution to the restored electrolyte.
41. The method of claim 31, wherein neutralizing a portion of the
aged electrolyte with an electrochemical device comprises:
receiving the aged electrolyte solution in an input chamber; urging
negative sulfate ions to diffuse through an anionic membrane
towards an anode into an anode chamber; urging positive copper ions
to diffuse through a cationic membrane from a copper feed chamber
into the aged electrolyte solution; urging positive hydrogen ions
to diffuse through a bipolar membrane towards a cathode from the
aged electrolyte solution into an isolation chamber; urging
negative hydroxide ions to diffuse through the bipolar membrane
towards an anode from the isolation chamber into the aged
electrolyte; and removing a copper sulfate solution from the
concentration chamber.
42. The method of claim 31, wherein the urging steps comprise
applying an electrical bias across the electrochemical device.
43. The method of claim 31, further comprising circulating a
sulfuric acid solution through the cathode chamber, the isolation
chamber, and the anode chamber.
44. The method of claim 31, further comprising circulating a copper
sulfate solution through the copper feed chamber.
45. The method of claim 31, wherein neutralizing a portion of the
aged electrolyte with an electrochemical device comprises:
receiving the aged electrolyte solution in an input chamber; urging
negative sulfate ions to diffuse through an anionic membrane
towards an anode in the anode chamber; urging positive hydrogen
ions to diffuse through a bipolar membrane towards a cathode from
the aged electrolyte into a purification chamber; urging negative
hydroxide ions to diffuse through a bipolar membrane from the
purification chamber into the aged electrolyte; and removing a
copper sulfate solution from the concentration chamber.
46. The method of claim 45, wherein the urging steps comprise
applying an electrical bias across the electrochemical device.
47. The method of claim 45, further comprising circulating a
sulfuric acid solution through the cathode chamber, the
purification chamber, and the anode chamber.
48. The method of claim 45, further comprising passing the copper
sulfate solution through an electrodialysis cell to further remove
contaminants and add copper ions to the solution.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to correcting the
concentration of semiconductor electrolyte solutions.
[0003] 2. Description of the Related Art
[0004] Metallization for sub-quarter micron sized features is a
foundational technology for present and future generations of
integrated circuit manufacturing processes. In devices such as
ultra large scale integration-type devices, i.e., devices having
integrated circuits with more than a million logic gates, the
multilevel interconnects that lie at the heart of these devices are
generally formed by filling high aspect ratio interconnect features
with a conductive material, such as copper or aluminum.
Conventionally, deposition techniques such as chemical vapor
deposition (CVD) and physical vapor deposition (PVD) have been used
to fill these interconnect features. However, as interconnect sizes
decrease and aspect ratios increase, void-free interconnect feature
fill via conventional metallization techniques becomes increasingly
difficult. As a result thereof, plating techniques, such as
electrochemical plating (ECP) and electroless plating, for example,
have emerged as viable processes for filling sub-quarter micron
sized high aspect ratio interconnect features in integrated circuit
manufacturing processes.
[0005] In an ECP process sub-quarter micron sized high aspect ratio
features formed on a substrate surface may be efficiently filled
with a conductive material, such as copper, for example. ECP
plating processes are generally two stage processes, wherein a seed
layer is first formed over the surface features of the substrate,
and then the surface features of the substrate are exposed to an
electrolyte solution while an electrical bias is simultaneously
applied between the substrate and an anode positioned within the
electrolyte solution. The electrolyte solution is generally rich in
ions to be plated onto the surface of the substrate. Therefore, the
application of the electrical bias causes these ions to be urged
out of the electrolyte solution and to be plated as a metal on the
seed layer. The plated metal, which may be copper, for example,
grows in thickness and forms a copper layer that fills the features
formed on the substrate surface.
[0006] In order to facilitate and control this plating process,
several additives may be utilized in the electrolyte plating
solution. For example, a typical electrolyte solution used for
copper electroplating may consist of copper sulfate solution, which
provides the copper to be plated, having sulfuric acid and copper
chloride added thereto. The sulfuric acid may generally operate to
modify the acidity and conductivity of the solution. The
electrolytic solutions also generally contain various organic
molecules, which may be accelerators, suppressors, levelers,
brighteners, etc. These organic molecules are generally added to
the plating solution in order to facilitate void-free super-fill of
high aspect ratio features and planarized copper deposition.
Accelerators, for example, may be sulfide-based molecules that
locally accelerate electrical current at a given voltage where they
absorb. Suppressors may be polymers of polyethylene glycol,
mixtures of ethylene oxides and propylene oxides, or block
copolymers of ethylene oxides and propylene oxides, for example,
which tend to reduce electrical current at the sites where they
absorb (the upper edges/corners of high aspect ratio features), and
therefore, slow the plating process at those locations, which
reduces premature closure of the feature before the feature is
completely filled. Levelers, for example, may be nitrogen
containing long chain polymers, which operate to facilitate planar
plating. Additionally, the plating bath usually contains a small
amount of chloride, generally between about 20 and about 60 ppm,
which provides for adsorption of suppressor molecules on the
cathode, while also facilitating proper anode corrosion.
[0007] Although the various organic additives facilitate the
plating process and offer a control element over the interconnect
formation processes, they also present a challenge, as the
additives are known to eventually break down and become contaminate
material in the electrolyte solution. Conventional plating
apparatuses have traditionally dealt with these organic
contaminants via bleed and feed methods (periodically replacing a
portion of the electrolyte), extraction methods (filtering the
electrolyte with a charcoal filter), photochemical decomposition
methods (using UV in conjunction with ion exchange and
acid-resistant filters), and/or ozone treatments (dispensing ozone
into the electrolyte). However, these conventional methods are
inefficient, expensive to implement and operate, or bulky, and may
generate hazardous materials or other kinds of contaminants as
byproducts.
[0008] Furthermore, conventional systems may utilize a soluble
metal anode to provide a continuous supply to metal ions for
electrolyte replenishment. However, anode dissolution has
disadvantages such as undesirable side products, e.g., sludge and
copper ball formation, and undesirable side effects, e.g., anode
passiviation, non-uniform anode dissolution, and
consumption/breakdown of organic additives. Therefore, there is a
need for a method and apparatus that minimize the formation and
effects of contaminants in semiconductor electroplating baths,
wherein the method and apparatus addresses the deficiencies of
conventional devices.
SUMMARY OF THE INVENTION
[0009] Embodiments of the invention generally provide an
electrochemical plating system having an anolyte compartment and a
catolyte compartment, wherein the anolyte compartment has an
anolyte inlet and an anolyte drain, and a membrane disposed between
the anolyte compartment and the catolyte compartment, wherein the
membrane is selective to positively charged ions, e.g., hydrogen
ions and copper ions. Embodiments of the invention further provide
a catolyte storage unit in fluid communication with the catolyte
inlet and an electrochemical device in fluid communication with the
catolyte compartment, the electrochemical device being configured
to correct an catolyte concentration.
[0010] Embodiments of the invention further provide a method for
plating copper. The method generally includes supplying an
electrolyte solution to a copper plating cell, plating copper onto
a substrate in the plating cell with the electrolyte solution,
removing aged electrolyte solution from the plating cell, and
correcting a catolyte concentration in the aged electrolyte
solution with an electrochemical device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof, which
are illustrated in the appended drawings. It is to be noted,
however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be
considered limiting of its scope, for the invention may admit to
other equally effective embodiments.
[0012] FIG. 1 illustrates an exemplary plating system incorporating
an electrochemical membrane device (ELDC) cell of the
invention.
[0013] FIG. 2 illustrates a schematic view of an exemplary ELDC
cell of the invention.
[0014] FIG. 3 illustrates a schematic view of another exemplary
ELDC cell of the invention.
[0015] FIG. 4 illustrates a schematic view of another exemplary
ELDC cell of the invention.
[0016] FIG. 5 Illustrates a schematic view of another exemplary
ELDC cell of the invention.
[0017] FIG. 6 Illustrates a schematic view of another exemplary
ELDC cell of the invention.
[0018] FIG. 7 illustrates an exemplary plating system incorporating
an ELDC cell and an electrodialysis cell (EDC).
[0019] FIG. 8 illustrates an exemplary embodiment of a plating
system incorporating an EDLC system wherein the concentration of
acid is decreased while the concentration of copper is
simultaneously increased.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] FIG. 1 illustrates an exemplary plating system 100 of the
present intention. Plating system 100 generally includes a plating
cell 101, which may be an electrochemical plating (ECP) cell for
copper superfill plating or another electroplating cell
configuration known in the semiconductor art. The plating cell 101
generally includes an anolyte inlet 105 configured to deliver an
anolyte, e.g., a plating processing fluid, to the plating cell 101,
and an anolyte outlet or drain 106 configured to retrieve anolyte
from plating cell 101. The anolyte is delivered to the plating cell
101 via inlet 105, which is in fluid communication with an anolyte
storage unit 102. A fluid pump 104 is generally positioned between
the anolyte storage unit 102 and the plating cell 101 and is
configured to deliver the anolyte to plating cell 101 upon
actuation thereof. The anolyte generally is contained in the
storage unit 102 and an anolyte compartment 108 with an anode 122
disposed therein. The anode 122 may generally be soluble, e.g., a
copper anode, or insoluble, e.g., platinum. The anolyte compartment
108 is generally separated from a catolyte compartment 110 having a
cathode, e.g., substrate, disposed therein, by a cation exchange
membrane 112.
[0021] An insoluble anode eliminates the formation of undesirable
side products and effects generally associated with soluble anodes.
However, soluble copper anodes do not require electrochemical
devices, which are designed to neutralize the excess of acid
generally forming on the insoluble anode. Instead, deionized water
is generally added to storage unit 102 to compensate for the loss
of water transported from the anolyte into the catolyte along with
copper ions.
[0022] The anolyte generally includes copper sulfate and a minimal
amount of sulfuric acid, e.g., an amount sufficient to provide an
anolyte pH of from about 2 to about 6. When the pH of the anolyte
is less then 2, the hydrogen ion concentration migrating to the
catolyte compartment is small, i.e., less than about 10 to about
100 times the concentration of copper ions migrating to the
catolyte compartment. The catolyte, e.g., a copper superfill
electrolyte, generally includes copper sulfate, sulfuric acid,
copper chloride, and additives to aid in plating, such as
accelerators, suppressors, and levelers. The cation exchange
membrane 112 generally is selective to positively charged ions,
e.g., hydrogen ions (H.sup.+) and copper ions (Cu.sup.2+);
therefore the H.sup.+ and Cu.sup.2+ migrate from the anolyte
compartment to the catolyte compartment. The H.sup.+ concentration
migrating to the catolyte compartment is very small, i.e., less
than 1000 times the concentration of Cu.sup.2+ migrating to the
catolyte compartment. The Cu.sup.2+ migration is generally
necessary to compensate for copper losses in the catolyte solution
due to copper plating. As a result of copper migration, the anolyte
copper concentration decreases and becomes more acidic over time.
Embodiments utilizing a soluble anode generally have a constant
anolyte acidity over time. Additionally, the H.sup.+ penetrating
the membrane slowly effects the catolyte concentration. Therefore,
electrochemical membrane devices (ELDC) are included in embodiments
of the invention to correct the anolyte and catolyte concentrations
(which may collectively be referred to as electrolyte in the
embodiments below).
[0023] The anolyte outlet 106 may be in fluid communication with an
input of the ELDC 103, which may have an output thereof, that is in
fluid communication with the anolyte storage unit 102. The cell 101
further includes a catolyte outlet 114 configured to retrieve
catolyte from the catolyte compartment 110. The catolyte is
recirculated to the catolyte compartment 110 through a catolyte
inlet 116, which is in fluid communication with a catolyte storage
unit 118. The catolyte passing from the catolyte outlet 114 to the
catolyte storage unit 118 may pass through a second ELDC 120
configured to correct the catolyte concentration.
[0024] Generally, the EDLC chambers 103 and 120, hereinafter
referred to only in terms of ELDC 120, are configured to receive a
portion of the used electrolyte returning from plating cell 101 to
anolyte storage unit 102. Generally the same ELDC chamber may be
used for chamber 103 and 120, with the exception that the catolyte
purity requirement may be higher than that for the anolyte, as the
catolyte should have all solids and contaminants removed before
reentry to the catolyte chamber, e.g., the copper electrode anode
utilized in one or more embodiments discussed below generally is
not in direct contact with catolyte to be corrected. Further, ELDC
cells utilized in the anolyte loop generally do not include bipolar
exchange membranes because copper hydroxide forms on the membrane
causing the membrane to fail.
[0025] The received portion of aged electrolyte is neutralized
within the ELDC 120 resulting in a restored electrolyte, which may
then be reintroduced into the anolyte storage unit 102 for
subsequent use in plating operations. The restored portion of the
electrolyte may generally include one or more concentrated salts
and acids that were originally present in the electrolyte and that
are generally free of contaminants resulting from organic additive
breakdown in the electrolyte. Although the exemplary ELDC
illustrated in FIG. 1 receives the entire aged electrolyte passing
through outlet 106, it is contemplated that various configurations
of ELDCs may be implemented, which may receive only a portion of
the used electrolyte.
[0026] FIG. 2 illustrates a schematic view of an exemplary ELDC 120
of the present invention. The exemplary ELDC 120, for example, may
be implemented into an ECP system configured to plate copper onto
semiconductor substrates. The exemplary ELDC 120 generally includes
an outer housing 201 configured to hold or confine the essential
elements of ELDC 120. A first end of housing 201 generally includes
a copper anode source 203, while a second end of housing 201
generally includes a cathode source 202. Anode source 203 and
cathode source 202 are generally positioned on opposite/opposing
ends of housing 201. The volume between cathode source 202 and
anode source 203 within housing 201 generally includes a plurality
of ELDC chambers, wherein the ELDC chambers generally include an
anode chamber 204 and a cathode chamber 205 corresponding to the
anode or cathode positioned in the respective end of housing 201. A
selectively permeable membrane 210 individually separates the
respective chambers 204, 205.
[0027] These membranes may be one of many commercially available
membranes. For example, Tokuyama Corporation manufactures and
supplies various hydrocarbon membranes for electrodialysis and
related applications under the trade name "Neosepta."
Perfluorinated cation membranes, which are stable to oxidation and
useful when it is necessary to separate an insoluble anode
compartment by a cation membrane, are generally available from
DuPont Co as Nafion membranes N-117, N-450, or from Asahi Glass
Company (Japan) under the trade name Flemion as Fx-50, F738, and
F893 model membranes. Asahi Glass Company also produces a wide
range of polystyrene based ion-exchange membranes under the trade
name Selemion, which can be very effective for
concentration/desalination of electrolytes and organic removal
(cation membranes CMV, CMD, and CMT and anion membranes AMV, AMT,
and AMD). There are also companies that manufacture similar
ion-exchange membranes (Solvay (France), Sybron Chemical Inc.
(USA), Ionics (USA), and FuMA-Tech (Germany) etc.). Further, in
order to minimize the penetration of copper ions into cathode
compartment, it may be helpful to separate this compartment by a
bipolar ionexchange membrane that is made from cation and anion
membranes compiled together. Bipolar membranes, such as models
AQ-BA-06 and AQ-BA-04, for example, are commercially available from
Aqualitics (USA) and Asahi Glass Co.
[0028] In a first embodiment of the invention, as illustrated in
FIG. 2, a membrane 210, which is selective and penetrable
preferably to univalent cations, especially to H.sup.+, separates
the respective chambers 204, 205. Cathode chamber 205 may be
supplied with a sulfuric acid solution via conduit 214, which may
operate to circulate the acid solution through the respective
chamber.
[0029] In operation, used electrolyte from a plating system is
delivered to anode chamber 204 via conduit 208, which may be in
communication with an electrolyte drain of an ECP cell. An
electrical bias is applied across ELDC cell 120 via anode 203 and
cathode 202. Generally the voltage drop between the cathode and
anode is from about 0.4 volts to about 1.5 volts. The use of a
soluble anode in the ELDC cell removes the need for a soluble anode
in the ECP cell, as the ELDC cell serves to replenish the copper in
the anolyte, remove acid, and facilitate anode maintenance. As a
result, anode by-products will not permeate the cation exchange
membrane to effect plating in the catolyte chamber.
[0030] The application of the electrical bias across ELDC cell 120
operates to urge ions in the aged electrolyte solution towards the
respective poles, i.e., positive ions will be urged in the
direction of the cathode, while negative ions will be urged in the
direction of the anode. Therefore, the disassociated copper ions
from the soluble copper anode 203, which are generally illustrated
as Cu.sup.2+ in FIG. 2, are urged in the direction of cathode 202
into the aged electrolyte solution. Similarly, disassociated
hydroxide ions, which are generally illustrated as OH.sup.-, are
urged in the direction of anode 203. The copper ions supplement the
reduced concentration of copper in the electrolyte and the
hydroxide ions neutralize the excess acid present in the
electrolyte. In addition, the bipolar membrane allows for removal
of H+ ions from the aged electrolyte to further neutralize the
excess acid. The formed acidic copper sulfate solution may then be
removed from anode chamber 204 and re-circulated into the plating
system (or an electrolyte solution tank, etc.), as
CuSO.sub.4/H.sub.2SO.sub.4 are primary elements of an electrolyte
solution for a copper electroplating system. Therefore, ELDC 120
generally operates to receive aged electrolyte from a plating
system and separate viable components (copper sulfate and sulfuric
acid) from the aged electrolyte for reuse in the plating
system.
[0031] FIG. 3 illustrates another embodiment of the invention. In
this embodiment, aged electrolyte is supplied to ELDC cell 120 via
conduit 208. Conduit 208 supplies the aged electrolyte into an
input cell or chamber 300 in the ELDC cell 120. While the aged
electrolyte is being supplied to the input chamber 300, an
electrical bias is applied across ELDC cell 120 via cathode 202 and
anode 203. ELDC 120 further includes 2 selectively permeable
membranes 302 and 304, which are generally cation exchange
membranes to allow ionic transfer from the anode 203 to the cathode
202. Anode chamber 204A is supplied with copper sulfate solution
and cathode chamber 205A may be supplied with a sulfuric acid
solution via conduit 214.
[0032] In operation, the disassociated copper ions in the aged
electrolyte solution are urged in the direction of cathode 202 into
the aged electrolyte solution of input chamber 300. Similarly,
positive hydrogen ions (H.sup.+) are urged in the direction of the
cathode 202 into the cathode chamber 205A. Furthermore, although
Cu.sup.2+ also penetrates the membrane 304, the amount is
negligible because the rate of H.sup.+ migrating to the cathode
chamber 205A is about 100 times greater than the copper ion
migration. To eliminate copper migration into the cathode chamber
205A, a membrane selective to H.sup.+, for example, the Neosepta
CMS membrane, may be used to separate the cathode chamber and the
input chamber. To even further eliminate the copper migration,
membrane 304 may be a bipolar membrane. The use of the bipolar
membrane further provides hydroxide migration from the cathode
chamber 205A to the input chamber 300 to further neutralize the
acid. More particularly, the positive copper and hydrogen ions in
input chamber 300 are urged towards cathode 202, and are allowed to
pass into the neighboring chambers, as the membranes separating
chambers 204A, 300, and 205A are cationic membranes, which may
generally be configured to transmit the respective positive ions
therethrough in the direction of the cathode 202.
[0033] FIG. 4 illustrates an alternative embodiment of the
invention. This embodiment varies from that illustrated in FIG. 3
in that only excess acid is extracted from the aged electrolyte.
Therefore, anode 203 is insoluble and anode chamber 204A is
supplied with a sulfuric acid solution via conduit 406. The
sulfuric acid is removed from anode chamber via conduit 406.
Membrane 302 is generally an anionic membrane that allows
negatively charged sulfate ions (SO.sub.4.sup.-) to migrate from
the aged electrolyte to the anode chamber 204A in the direction of
the anode 203.
[0034] Similar to the alternative embodiment illustrated in FIG. 3,
membrane 304 is a bipolar membrane, whereby H.sup.+ migrates from
input chamber 300 to cathode chamber 205A and OH.sup.- migrates
from cathode chamber 205A to input chamber 300. Since no additional
copper is added to the aged electrolyte to correct the
concentration, concentrated copper sulfate solution is generally
added to the ELCD output 402. A sensor 404 provides acid control of
the copper and hydrogen concentration in the output 402. The sensor
404 provides acid concentration control by interrupting the current
flowing when the conductivity of the output 402 falls below a
predetermined level. The predetermined level may vary depending on
system requirements. Alternatively, the concentration of acid in
the output 402 may be regulated by a controller (not shown). The
controller may regulate the ELCD 120 current passing between
cathode and anode depending on current flowing through the copper
solution in the plating cell 101. An additional controller (not
shown) may generally control the concentration of copper sulfate in
the output 402, thereby determining the amount of concentrated
copper sulfate solution to be added to the output 402.
[0035] FIG. 5 illustrates another embodiment of an exemplary ELDC
500 of the invention that generally corrects both acid and copper
ion concentration in the aged electrolyte. ELDC 500 is similarly
constructed to ELDC 120, in that ELDC 500 includes an anode chamber
502 and a cathode chamber 504. In similar fashion to ELDC 120, an
inlet 512 is used to communicate used or aged electrolyte from a
plating cell, such as a copper ECP cell, into the input chambers
506 of ELDC 500. Immediately outward of the input chambers 506 are
individual copper feed chambers 508. Copper feed chambers 508
generally include a fluid inlet and a fluid outlet configured to
receive and expel a circulating fluid, which may be a copper
sulfate solution. In this configuration, a diluted, e.g., from
about 0.01 M to about 0.1 M, sulfuric acid solution may be
circulated between an isolation chamber 510 positioned in the
anodic direction of the feed chamber 508 and the anode chamber 502
and a cathode chamber 504.
[0036] The membrane structure of ELDC 500 is similar to the
membrane structure of ELDC 120. However, ELDC 500 includes a slight
variation on the membrane configuration in order to accommodate the
additional chambers. More particularly, the membrane structure
generally follows an alternating sequence, i.e., from left to
right, an anionic membrane, then a cationic membrane, then a
bipolar membrane, then anionic membrane, etc.
[0037] In operation, ELDC 500 operates similarly to ELDC 120
illustrated in FIG. 2, as the aged electrolyte is supplied to input
chambers 506 via conduit 512, while electrical bias is applied
between cathode 516 and anode 518. However, rather than a soluble
copper anode electrode, an insoluble anode electrode is used to
minimize the anode maintenance and the copper sulfate solution is
corrected by copper ion addition. The copper ions may be fed to the
aged electrolyte from a fresh copper sulfate solution, or by dry
copper sulfate salt via conduit 524. The depleted copper sulfate
solution may then be retrieved from the feed chambers 508 via
conduit 520 for replenishment. The application of the electrical
bias causes positively charged ions in the aged electrolyte
solution to migrate towards the cathode 516, while negatively
charged ions are urged to migrate towards the anode 518. The
configuration of cationic, anionic, and bipolar membranes operates
to transport positive copper ions, positive hydrogen ions, negative
hydroxide ions, and negatively charged sulfate ions between the
respective membranes and into the desired chambers as illustrated
in FIG. 5. The positive copper ions and the negative hydroxide ions
combine to form renewed concentrated copper sulfate, which may then
be extracted from ELDC 500 for reuse in a copper plating system.
The anode 502, cathode 504, and isolation chambers 510 have a
dilute sulfuric acid solution circulating between the chambers. The
acid retrieved from chambers 502, 504, and 510 via conduit 514
accumulates in tank 522. Periodically, water may be added to the
tank 522 so that the acid remains diluted and the excess volume of
acid is discarded where it may be neutralized or disposed of. The
diluted acid is then recirculated to chambers 502, 504, and 510 via
conduit 526.
[0038] FIG. 6 illustrates another embodiment of an exemplary ELDC
600 of the invention. ELDC 600 is similar in structure to ELDC 500
and ELDC 120 discussed above. As illustrated in FIG. 6, ELDC 600
generally includes a chamber housing having a cathode 604
positioned on a first end and anode 605 positioned on a second end.
A plurality of chambers are positioned between the respective
cathode 604 and anode 605. However, ELDC 600 includes a different
configuration of membranes. More particularly, ELDC 600 generally
alternates between anionic and bipolar membranes, with the anionic
membranes bounding the cathode 604 and anode chambers 602.
[0039] The plurality of chambers include input chambers 601
configured to receive aged electrolyte therein via conduit 606.
Anode and cathode chambers 602 and 604 and purification chamber 603
are fed by diluted sulfuric acid 612. As in the embodiment of FIG.
5, the output 608 of chambers 604 and 603 accumulate in tank 522,
wherein water may be added to the output 608 to retain diluted
sulfuric acid solution. In operation, ELDC 600 receives aged
electrolyte 606, which generally includes positive copper and
hydrogen ions, negative sulfate ions, and variously charged
contaminated ions in input chambers. The aged electrolyte 606 flows
through the input chambers 601, as indicated by the arrows
illustrated in FIG. 6. As the aged electrolyte 606 flows through
the input chambers 601, the respective positive and negative ions
are drawn toward the cathode 604 and anode 605 according to their
polarity, as described in previous embodiments. Therefore, as a
result of the electrical potential applied across ELDC 600 by the
cathode 604 and anode 605, the output 610 input chambers 601
generally consists of primarily concentrated copper sulfate and
sulfuric acid (with a concentration determined by individual system
requirements). Like previous embodiments, the output 610 of ELDC
600 is corrected by the addition of copper sulfate solution. The
present embodiment has an advantage over conventional devices and
previous mentioned embodiments. The ELCD 600 is more compact and
the surface area of the electrodes is small, resulting in a lower
cost for the same performance.
[0040] The embodiments illustrated in FIGS. 3 and 5 are generally
used for the correction of copper electrolytes with a high
concentration of copper sulfate, e.g., from about 30 g/L to about
65 g/L of copper ions. In contrast, the embodiments illustrated in
FIGS. 4 and 6 are generally used to correct the concentration of
electrolytes with a relatively low concentration of copper sulfate.
However, an alternative embodiment of the invention contemplates
the combination of the ELDC of FIG. 6 to correct (increase) low
concentration of copper sulfate with an electrodialysis cell (EDC)
in order to correct electrolytes with a high concentration of
copper sulfate, as illustrated in FIG. 7. Additionally,
combinations of the EDLC cells may be combined to produce desired
concentration correction.
[0041] Plating system 100A generally includes the components of
system 100, with the exception that EDC 700 is generally configured
to receive a portion of the electrolyte being returned from ELDC
600 to catolyte storage unit 118. The received portion of
electrolyte is separated within EDC 700 into a usable fluid portion
and a discardable fluid portion, wherein the usable fluid portion
may then be reintroduced into the catolyte storage unit 118 for
subsequent use in plating operations. The usable portion of the
electrolyte may generally include one or more concentrated salts
and acids that were originally present in the plating solution and
that are generally free of contaminants resulting from organic
additive breakdown in the plating solution. The discardable portion
of the plating solution, which generally represents one or more
dilute acids in conjunction with plating solution additives,
contaminants and traces of copper, is separately output from EDC
700 and captured for disposal or neutralization thereof without
returning to the catolyte storage unit 118. The usable and
discardable portions of the plating solution are generally
separated by alternating anionic and cationic membranes. Copper
sulfate solution generally flows between anionic and cationic
membranes and sulfuric acid generally flows between anionic
membranes and the anode and cathode.
[0042] FIG. 8 illustrates an exemplary embodiment of a plating
system 100B incorporating an EDLC system wherein the concentration
of acid is decreased while the concentration of copper is
simultaneously increased utilizing the EDLC chamber 500 detailed in
FIG. 5. Plating system 100B generally includes the components of
system 100, with the exception that ELDC 103 is generally replaced
by a filter 802 and column 801. Generally copper oxide or copper
hydroxide is utilized to correct the copper concentration. Copper
oxides dissolve only in acidic solutions as a result of reaction
with the acid. After contact with the aged electrolyte, the acid
formed on the insoluble anode disappears and the copper
concentration returns to its original concentration. The copper
oxides, generally in powder or granule form, are placed in column
801 and the aged anolyte exiting the anode chamber 108 passes
through column 801 and filter 802. The filter 802 protects the
anolyte loop from undesirable copper oxide particles. This
embodiment may generally be utilized when the concentration of
copper in the anolyte need not be precisely controlled.
[0043] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *